Spring ligament insufficiency and hallux valgus as an independent risk factors for first ray instability.

Introduction: First ray instability (FRI) arising from failed plantar/interosseous ligaments is strongly associated with planovalgus, leading to synovitis and deformity. Our hypothesis is that proximal spring ligament insufficiency (SLI) drives secondary FRI in the absence of hallux valgus (HV) and may be an independent risk factor.

Methods: Patients with FRI, screened by Klaue's test, were recruited.